We switch gears now and get the latest on Oscar Pistorius. A surprising battle opening up in the trial, rising the suspect that he suffers from a mental disorder. Reporter: It was the biggest turn in the saga in the Pistorius trial. I indicated yesterday that I'd bring in an application. I'm ready to do so. Reporter: Gerrie nel, requesting psychological evaluation of Pistorius, saying -- We will argue that the accused was not the most impressive witness. We will argue that his evidence be rejected. Isn't that the only reason why a psychiatrist is consulted after his evidence? Reporter: His defense witness, psychiatrist Merrill Forrester, diagnosed him with mental disorder, saying how he affected that night and could play a role in sentencing. There could be another explanation. That it was just lying. Yeah. He could just be lying to you. Reporter: And he's a danger to society. People suffer from generalized anxiety disorders are not dangerous as much. People with generalized anxiety disorders probably shouldn't have firearms. That creates the element of dangerousness. Reporter: And it got worse. Under cross, Pistorius who pleaded not guilty, waffled about why he shot at the door. Saying, among other things, he shot accidentally. It's not what he told the psychiatrist. He said to you, he fired at the noise. At the noise. You know that he said in court that, he denied he fired at the noise. It would appear that there are inconsistencies. Reporter: Now, the defense, forced into a position where it has to prove Pistorius' sanity. Saying he is not delusional. Negating the testimony of what should have been the star witness. For 24 hours, Oscar Pistorius has to wait and learn if he has to be sent to a mental institution for as many as 30 days.

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